1. Field of the Invention
This invention relates to a combination of transceivers operating in the ultra sonic frequencies used to monitor the activities of a child or The guardian's tranceiver emits a sonic warning signal whenever the child strays beyond a predetermined distance, when the child is immersed in water or when the child's transceiver is removed from the child.
2. Description of the Prior Art
Many devices have been proposed for the monitoring the location of a person carrying the device. Most of the prior art describes sophisticated radio frequency transmitters with associated receivers. U.S. Pat. No. 4,675,656 Narcisse, describes a radio frequency having a base unit transmitter that transmits a signal to a mobile receiving unit having a threshold circuit adjustable to a prescribed distance. The receiver producing a threshold output signal whenever the detected signal drops below the threshold level. U.S. Pat. No. 4,736,196 McMahon, describes a radio frequency system for monitoring the location of an individual having a band incorporating a transmitter strapped to the wrist or ankle.